Generally, hand-held hand-powered sprayers such as finger pump sprayers and trigger sprayers achieve atomization by actuation of a finger pump or manually operable trigger which compresses a measured quantity of liquid and forces it under pressure through a swirl chamber and out an exit orifice. Hand-held hand-powered sprayers such as the small compressed air sprayers commonly used in lawn and garden applications rely on a pressurized volume of gas to similarly force liquid under pressure through a swirl chamber and out an exit orifice. In both cases, atomization is achieved as an end result of hand force being applied to the liquid (directly in the case of the trigger sprayer, indirectly in the case of compressed air sprayer). While this type of hydraulic (or pressure) atomization is an effective method for spraying liquids of low viscosity, it is generally inadequate with respect to oils and other viscous liquids.
Because of their increased resistance to disintegration, high viscosity fluids are particularly difficult to atomize. Traditionally, these heavier fluids can be effectively sprayed only by using an external energy source and/or compressed air source (e.g., power painters), in very limited quantities through manually operated sprayers/dispensers that provide mechanical advantage (e.g., fine mist finger pump sprayers that incorporate pre-compression operation), or through pressurized packaging using propellants and/or other gasses (e.g., aerosols). In combination with these methods, thinning agents and/or other additives are often added to the product to further assist atomization of the liquid.
Those systems that rely on external energy and/or compressed air are generally costly, cumbersome and inappropriate for most small applications. Those that rely on mechanical advantage to hydraulically atomize viscous fluids generally can dispense only very small quantities per actuation, may require excessive hand force, and are subject to clogging due to the small diameter passageways the method requires.
Within the context of hand-held, hand-actuatable devices, aerosols succeed in being able to effectively atomize liquids including those of moderately high viscosity. But many drawbacks have been associated with aerosol product delivery systems. Included in these drawbacks are that these systems are often: environmentally hazardous (i.e., they contain HCFCs, CFCs, VOCs); non-recyclable; costly; frequently used in conjunction with thinning agents, alcohols and other synthetic additives that are generally undesirable because they are volatile and can contaminate product purity; and prone to overspray.
While there exist hand-held sprayer devices that utilize air as a secondary agent of atomization (such as U.S. Pat. No. 5,110,052 to Graf et al. issued May 5, 1992) where a volume of air acts on a volume of liquid that has already been hydraulically atomized, there have not been successful attempts at providing hand-held, hand-powered pneumatic sprayers for viscous fluids. Atomization as used herein refers to the mechanical subdivision of a liquid. Pneumatic atomizers as used herein refers to atomizers in which the energy of the gas, generally air, is the primary force causing liquid disintegration.
Additionally, there have been vapor tap sprayers wherein air is introduced into a liquid stream prior to the stream exiting the discharge orifice. In these systems, the liquid/air mix is forced through the discharge orifice under pressure in what remains an essentially hydraulic atomization process. While this approach is effective in some applications, the consistency of the spray is prone to fluctuate as the gas pressure which introduces the gas into the stream is reduced because of draw down during spraying. It is also not clear that air can be efficiently introduced in this way to a stream of viscous media.
Also, dispensing systems are known which have the capability to both spray liquids and pour liquids. An example of such a dual dispensing system is shown in U.S. Pat. No. 4,618,076 issued to Silvenis, Oct. 21, 1986. Such known systems entail a dual dispensing bottle having two openings at the top, one to which a conventional trigger sprayer is attached, the other to which a plug-like apparatus is attached. This system is disadvantageous in that it necessitates specially molding a bottle rather than providing a trigger with an integrated pour spout which can be used interchangeably on a wide range of readily available containers. Bottle as used herein is used interchangeably with container and refers to a receptacle formed from any variety of materials, having any size neck and mouth that can be plugged, corked or capped, wherein capped includes caps of the screw-twist type.
Thus, the discussion above shows recognized deficiencies existing in the field of hand-held, hand-powered sprayers. For instance, there remains a need in the art to provide a hand-held sprayer which can effectively spray viscous fluids such as cooking oils or the like without the use of complex machinery or environmentally undesirable propellants. It is also a goal in the art to provide a hand-held sprayer which provides suitable larger quantities of fluids without severe overspray and while maintaining a hand-held size. It is further a goal to provide a hand-held sprayer having an integrated pour spout which is re-usable and interchangeable and can be attached to any conventional bottle. It also a goal to provide such sprayers in a construction which is simple and cost-efficient to manufacture and use.